Miniature image acquistion system using a scanning resonant waveguide

ABSTRACT

A minimally invasive, medical, image acquisition having a flexible optical fiber serving as an illuminating wave guide. In one resonance mode, the distal end of the fiber is a stationary node. The fiber includes a lens at the distal tip which collimates emitted light. A scan lens is positioned off the end of the fiber. The relative magnifications of the lenses and the relative positions determines the pixel resolution. In particular, the illumination fiber outputs a light beam or pulse which illuminates a precise spot size. A photon detector detects reflected photons from the object, including the spot. Pixel resolution is determined by the area of the illumination spot (and thus the lens configuration), rather than an area sensed by the detector.

CROSS REFERENCE TO RELATED APPLICATIONS

This invention is related to U.S. Provisional Patent Application Ser.No. 60/138,404 filed Jun. 8, 1999 for “Miniature Image AcquisitionSystem Using a Scanning Resonant Waveguide.” The content of thatapplication is incorporated herein by reference and made a part hereof.

BACKGROUND OF THE INVENTION

This invention relates to fiber optic scanning devices, such as fiberoptic image acquisition devices and fiber optic image display devices,and more particularly to a fiber optic scanning device which achieves ahigh image resolution and a wide field of view using a flexible fiber ofvery small diameter.

Fiber optic image acquisition devices include endoscopes, boroscopes andbar code readers. An endoscope is an imaging instrument for viewing theinterior of a body canal or hollow organ. Entry typically is through abody opening. A boroscope is an imaging instrument for viewing aninternal area of the body. Entry typically is invasive through a ‘bored’opening (e.g., a surgical opening).

There are rigid endoscopes and flexible endoscopes. Rigid endoscopes donot have a pixelated image plane. Flexible endoscopes are smaller andconventionally have a pixelated image plane. Flexible endoscopes,however, are unable to achieve the resolution and field of view of rigidendoscopes. But the rigid endoscopes are unable to be used in manyapplications where small size and flexible fibers and shafts arerequired.

The goal of any endoscope is high image quality in a small package,allowing minimal tissue trauma. In the growing field of minimallyinvasive surgical techniques, there is great demand for smallerendoscopes that match current image quality. In particular, the demandfor minimally invasive medical procedures has increased the demand forultrathin optical endoscopes. However, commercial flexible endoscopeshave a fundamental tradeoff of size versus image quality. The smallerthe endoscope diameter the lower the image resolution and/orfield-of-view (FOV), such that image quality deteriorates. Manyendoscopic techniques are not possible or become risky when very smallendoscopes are used because the doctor has insufficient visualinformation, i.e. small size and poor quality of images. Accordingly,there is a need for very small, flexible endoscopes with high resolutionand FOV. This fundamental tradeoff of a flexible image generator thathas both a very small diameter and has the high image quality is a majorlimitation in applications outside the human body, such as remotesensing.

Conventional flexible endoscopes and boroscopes include a large spatialarray of pixel detectors forming a CCD camera. Typically a bundle ofoptical fibers capture an image and transmit the image to the CCDcamera. To achieve a high resolution, wide field image, such CCD camerasoften include a pixel detector array of approximately 1000 by 1000detectors. For color fidelity it is common to include three such arrays,and where stereoscopic viewing is desired, this doubles to six arrays. Afiber is present for each pixel detector. Each fiber has a diametergreater than or equal to 4 microns. Thus, acquisition requires a spaceof greater than or equal to 4 microns per pixel. If a standard sVGAimage is desired (800×600 pixels), then a minimum diameter of just theimage conduit is greater than 3 mm. A 1000 by 1000 pixel detector arrayhas a diameter of at least 4 mm. For a VGA standard, resolution and/orfield of view is sacrificed by having fewer pixel elements in order toattain less than 3 mm overall diameter scopes. Reducing the diameter ofthe endoscope reduces the possible number of pixels, and accordingly,the resolution and field of view. Limits on diameter also limit theopportunity to access color images and stereoscopic images.

In the field of small (e.g., less than 3 mm dia.), flexible endoscopes,the scopes need to use the smallest pixel size, while still reducing thenumber of pixels, typically to (100×100). Note, these small flexibleendoscopes are found by surgeons to be too fragile, so as not to bewidely used. Instead doctors prefer small, but rigid-shafted (straight)endoscopes, greatly limiting their maneuverability and applicability.

In the field of large (e.g., greater than or equal to 4 mm dia.),flexible endoscopes, the scopes have a flexible shaft which is greaterthan or equal to 4 mm in diameter and typically include either a bundleof optical fibers or a small camera at the distal end to capture theimage. However, there is still a tradeoff between the desired 50-70° FOVand image resolution at the full potential of human visual acuity untilthe scope diameter reaches>10 mm.

U.S. Pat. No. 5,103,497 issued Apr. 7, 1992 of John W. Hicks discloses aflying spot endoscope in which interspacing among fiber optics isdecreased to reduce the overall diameter of the optical bundle. Ratherthan arrange a bundle of fibers in a coherent manner, in his preferredembodiment Hicks uses a multi-fiber whose adjacent cores are phasemismatched. The multi-fiber is scanned along a raster pattern, a spiralpattern, an oscillating pattern or a rotary pattern using anelectromagnetic driver. The illumination fibers, the viewing fibers orboth the illuminating fibers and the viewing fibers are scanned. In asimplest embodiment, Hicks discloses scanning of a single fiber (e.g.,either the illuminating or the viewing fiber).

Hicks uses a small bundle or a single fiber to scan an image plane byscanning the fiber bundle along the image plane. Note that the imageplane is not decreased in size. The smaller bundle scans the entireimage plane. To do so, the bundle moves over the same area that in priorart was occupied by the larger array of collecting fiber optics. As aresult, the area that Hicks device occupies during operation is the sameas in prior devices. Further, the core size of the fibers in Hicks'smaller bundle limits resolution in the same manner that the core sizeof fibers in the prior larger arrays limited resolution.

One of the challenges in the endoscope art is to reduce the size of thescanning device. As discussed above, the minimal size has been afunction of the fiber diameter and the combination of desired resolutionand desired field of view. The greater the desired resolution or fieldof view, the larger the required diameter. The greater the desiredresolution for a given field of view, the larger number of fibersrequired. This restriction has been due to the technique of sampling asmall portion of an image plane using a fiber optic camera element.Conventionally, one collecting fiber is used for capturing each pixel ofthe image plane, although in Hicks one or more fibers scan multiplepixels.

When generating an image plane, an object is illuminated by illuminatingfibers. Some of the illuminating light impinges on the object directly.Other illuminating light is scattered either before or after impingingon the object. Light reflected from the image plane is collected.Typically, the desired, non-scattered light reflected from anilluminated portion of an object is differentiated from the scatteredlight by using a confocal system. Specifically a lens focuses the lightreturning to the viewing fiber. Only the light which is not scatteredtravels along a direct path from the object portion to the lens and theviewing fiber. The lens has its focal length set to focus thenon-scattered light onto the tip of the viewing fiber. The scatteredlight focuses either before or after the viewing fiber tip. Thus, thedesired light is captured and distinguished from the undesired light.One shortcoming of this approach is that most of the illuminated lightis wasted, or is captured by surrounding pixel elements as noise, withonly a small portion returning as the non-scattered light used to definea given pixel.

SUMMARY OF THE INVENTION

According to the invention, a miniature image acquisition system havinga flexible optical fiber is implemented. The flexible optical fiberserves as an illuminating wave guide which resonates to scan emittedlight along a desired pattern. Preferably a single fiber is used for theillumination light. For multiple colors of illumination light, it ispreferred that the light from the respective color sources be combinedand passed through a distal tip of the single illuminating fiber foremission onto an object being viewed. In alternative embodimentsmultiple fibers, or concentric fibers, are used for the illuminationlight.

Rather than generating and sampling an image plane (i.e., in whichpixels ale spatially separated) as done for conventional flexibleendoscopes and the like, an image plane need not be generated to capturean image by the scanner of this invention. Instead pixels are acquiredtemporally, being separated in time. An advantage of this approach isthat image resolution is no longer limited by the detector size (e.g.,the diameter of the collecting fiber). According to one aspect of thisinvention, image resolution, instead, is a function of the illuminatingspot size. In particular image resolutions are improved by using a spotsize which is smaller than the diameter of the collecting device. In oneembodiment single-mode optical fibers are implemented which have smallergaussian beam profiles and smaller core profiles allowing generation ofsmaller spot sizes at the scanned site.

Because a pixel is detected as the received light within a window oftime, the photons detected at such time window come from the illuminatedspot. Another advantage of this invention is that the confocal problemoccurring in the prior art systems is avoided. Using a typical videorate, for example, to define the pixel time window sizes, one pixel iscollected every 40 nanoseconds. For the light of one pixel to interferewith the light from another pixel, the light of the first pixel wouldhave to bounce around approximately 20 feet on average (because lighttravels about 1 foot/nanosecond). For typical applications such lightwould have to bounce around in a space less than one cubic inch. Thatcorresponds to approximately 240 reflections. It is unlikely that thelight from one pixel will make 240 reflections before getting absorbed.Thus, the confocal problem is not significant.

According to one aspect of the invention, a distal portion of anilluminating fiber serves as a resonating waveguide. Such distal portionis anchored at an end proximal to the rest of the fiber, (e.g., referredto as the proximal end of the distal portion, or the proximal end of theresonating waveguide). The distal portion is free to deflect andresonate. The waveguide is flexible, being deflected along a desiredscan path at a resonant frequency. Light detectors are positioned at theend of the illuminating fiber, (e.g., in the vicinity of the anchoredproximal end of the distal portion). Note that collecting fibers may bepresent, but are not necessary. Further, the detectors may, but need nottrace a scan pattern.

During operation, the distal portion of the illuminating fiber isdeflected in a resonant mode. Because the proximal end of the distalportion is anchored, it serves as a stationary node. In one embodiment,the proximal end is the only node. An anti-node is present along thelength of the distal portion. According to another aspect of theinvention, in another embodiment there is at least one other stationarynode. In particular, the distal end of the distal portion of theresonating fiber also is a stationary node. At least one anti-nodeoccurs between the stationary nodes at the proximal end and distal end.Because a stationary node occurs at the distal end, the orientation ofthe distal end changes during optical scanning, but its position remainsalong an axis of the fiber (the axis being the straight orientation ofthe fiber while stationary). To define a frame of reference, considerthe inactive distal portion of the fiber extending straight in an axialdirection. Consider such axial direction a z-axis. Such z-axis is normalto an x-y plane. During deflection of the distal portion in which thedistal end is a stationary node, the distal end does not move within thex-y plane. Slight movement may occur along the z-axis, (due to bothaxial and lateral actuation of the cantilever), although in someembodiments it is substantially fixed along the z-axis.

An advantage of placing a stationary node at the distal end of thewaveguide is that the diameter of the endoscope or other illuminatingdevice need not be enlarged to encompass a swinging distal end (e.g.,the distal end is stationary in the x-y plane). By fixing the distal endin X-Y space, rather than swinging it as a point source of light along aline or arc in X-Y space, optical distortions are reduced in the distalscan plane. Further, rather than moving the distal end along an arc todefine the field of view, the position of the distal end issubstantially fixed while the orientation of the distal end changes withthe resonating motion of other regions of the resonating waveguide. Thechanging angular orientation of the fiber distal end defines the widthof the field of view which is scanned.

According to another aspect of the invention, one or more lenses areformed at the distal end of the waveguide by shaping the distal end.Alternatively, one or more lenses are fused, bonded, mounted orotherwise attached to the distal end (i.e., the distal tip) of theilluminating fiber. Preferably, the lenses do not extend beyond thecircumference and diameter of the fiber. The lenses are fixed relativeto the distal tip and move and change orientation with the distal tip.Such lens(es) serves primarily to collimate the emitted light, and incombination with one or more lenses, to reduce optical aberrations.Another lens (e.g., a scan lens or f-theta lens) is positioned beyondthe distal tip of the end of the fiber in the path of the emitted lightto focus the light on a desired object (or display area). In someembodiments this other lens seals the end of the scope, and is arefractive and/or diffractive optical element. Collimating the emittedlight and locating a stationary resonance node at the distal end enablesprecise control of the lateral position, size and depth of the focalpoint of the emitted light. As a result, image quality is improved.Further, the lenses at the distal tip and off the fiber end define theimage resolution of the scope.

An advantage of the invention is that flexibility of the fiber, a widefield of view and high resolution are achieved even for small, thinscopes due to the method in which pixels are obtained, the presence ofthe lenses and the manner of driving the fiber. Because pixels aremeasured in time series and not in a 2-D pixel array, it is notmandatory to have small photon detectors. The size of the detector isnot critical as in the prior scopes where many small detectors spanned alarge area. Therefore, a scope of this invention can be made smallerthan existing scopes while using fewer photon detectors that are largerthan the pixel detectors of standard scopes. According to the invention,as little as one photon detector may be used for monochrome imageacquisition and as few as single red, green and blue detectors may beused for full-color imaging. By adding matched stereo-pairs of red,green and blue detectors, the advantage of quasi-stereo imaging isachieved accentuating topography in the full-color images.

In some embodiments, device size is decreased without compromisingresolution or field of view by implementing a resonant mode much higherthan a fundamental resonance mode, wherein there are multiple stationarynodes, including a stationary node at the proximal end, at the distalend and at least one between the proximal end and the distal end.According to another aspect of the invention, scope size is reduced insome embodiments by implementing a waveguide drive system whichgenerates non-linear excitations to deflect the fiber in one dimensionso as to produce two dimensional fiber scanning patterns or rotationalscanning patterns. Further, size is reduced in some embodiments bytapering the distal end so as to reduce the scan path length. Even forthe embodiment in which the distal node is stationary, tapering thedistal end reduces mass allowing the fiber to vibrate at greateramplitudes resulting in increased scanning efficiency.

According to another aspect of the invention, in an image acquisitionsystem an image frame is displayed incrementally as the image isobtained. In particular, an entire image frame need not be capturedbefore such frame is displayed. Instead, a pipeline of acquired pixelsfor a given frame is being filled with acquired pixels while also beingemptied of displayed pixels.

According to another aspect of this invention, true stereoscopic viewingis achieved by either adding another scope and processing the requiredimage parallax for human viewing, or by adding an axial measurement fromthe scope to the target by range finding at each pixel position. Suchaxial measurement is a third image dimension which is processed togenerate stereo views.

According to another aspect of the invention, image resolution isaltered to create a ‘zoom’ mode by changing the sampling rate of thelight detectors and scaling the scanner drive input and the displayoutput, accordingly. Because no physical pixel-array with a fixed numberof detectors is used, pixelation of the image is based on sampling rateswhich can be varied dynamically to give dynamic zooming.

According to one embodiment of the invention, the image acquisitionsystem allows a person to view objects being scanned directly bydirectly viewing the photons scattered from the object. This differsfrom conventional image acquisition systems and other embodiments of theinvention in which the scattered light impinges upon photon detectors,which then transmit the photon stream. Such photon detectors includephotomultiplier tubes, silicon-based photodetectors, image storage media(e.g., film) and photoemissive media. Such photon detection is anintermediary step. By eliminating the intermediary step images of higherspatial resolution, contrast, color fidelity and temporal resolution areachieved. Such improvement occurs because the limited bandwidth of thedetectors and the introduction of noise into the image signal by thedetectors are avoided. Further, the photon detectors often sample theoptical image. In may cases the subsequent resampling and redisplayingof the object image will not match the spatial and temporal sampling ofthe human eye, further degrading the image. The shortcomings introducedby the photon detectors are avoided by displaying the original, oroptically amplified, pixel as it is acquired. In one embodiment thereflected light from the object for a given pixel impinges on acollector fiber. The received light from the collector fiber travelsalong the fiber to a retinal scanner which synchronously deflects thecollected light to an appropriate pixel location on the viewer's retina.The photons are routed from the object being viewed to the viewer's eyewithout being relayed by an intermediary storage device. In otherembodiments, the collected light for a given pixel is projected directlyonto an observation screen for viewing, or is synchronously registeredon a storage media. In each embodiment the image viewed or stored isbeing constructed synchronously pixel by pixel as the pixel light iscaptured. There is no need for intermediary storage of an entire frameof pixels before viewing or projection occurs.

According to another advantage of the invention, a high resolution, highfield of view, scanning, flexible fiber device is achieved. By locatingthe fiber resonant node at the distal end of the resonating waveguideportion of the fiber, a wide scanning angle is achieved in a relativelysmall fiber movement area. This allows for a wide field of view. Byusing a small spot size and by time capturing the detected light incorrelation to the illumination light, a high pixel resolution isachieved. With the small size and low cost components, a disposablescanning device is achieved. For example, a Micro-optical ElectroMechanical Systems (‘MEMS’) fabrication process may be used.

According to another advantage of the invention, a single scanning fiberwith a small flexible shaft provides (i) axial symmetry, (ii) a low costmethod of providing color fidelity, increased object contrast andincreased fluorescent contrast, and (iii) laser illumination useful forfluorescent imaging, medical diagnosis and laser surgery. These andother aspects and advantages of the invention will be better understoodby reference to the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a miniature image acquisition systemaccording to an embodiment of this invention;

FIG. 2 is a diagram of the illuminating subsystem of the imageacquisition system of FIG. 1;

FIG. 3 is a diagram of a collector subsystem and display portion of anembodiment of the image acquisition system of FIG. 1;

FIG. 4 is a diagram of a portion of another embodiment of the imageacquisition system of FIG. 1, including a detector subsystem, displaydevice and image storage device;

FIGS. 5A-C are diagrams of a resonant waveguide portion of theilluminating fiber of FIG. 2 in various resonance modes;

FIG. 5D is a diagram of a fiber's distal lens at varying orientationsaccording to the resonance mode of FIG. 5C;

FIG. 6A is a diagram depicting sampling of a small pixel area of animage plane according to a conventional technique in which the sampledarea defines the pixel size and pixel resolution;

FIG. 6B is a diagram depicting sampling of a large area according to anembodiment of this invention in which a smaller illuminated area withinthe large sampled area defines the pixel size and pixel resolution;

FIG. 7 is a diagram of the resonant waveguide and focusing lens showingpoints along a scan line and a corresponding illuminated spot;

FIG. 8 is a chart of the fiber drive system synchronization signal, theangular displacement of the fiber tip and the illuminated spot positionversus time;

FIG. 9 is a diagram of a scan line formed by constant illumination whichis continuously sampled, wherein the sampling result is divided in timeto derive N pixels;

FIG. 10 is a diagram of a scan line formed by constant illuminationwhich is periodically sampled, wherein each sample corresponds to one ofN pixels;

FIG. 11 is a diagram of a scan line formed by periodic pulsedillumination in which periodic sampling is performed in synchronizationwith the pulses to derive samples of N pixels;

FIG. 12 is a planar side view of a scope portion of the system of FIG.1;

FIG. 13 is a planar front view of the scope of FIG. 12;

FIG. 14 is a perspective view of the scope of FIG. 13 without an outersheath;

FIGS. 15A-C are planar views of a micro-optical electro mechanicalsystem (MEMS) embodiment of a scope portion of FIG. 1;

FIG. 16 is a perspective view of another embodiment of a scope portionof the system of FIG. 1, including a bimorph bender actuator and inwhich photodetectors are mounted to a disk which moves during actuationof the bender;

FIG. 17 is a perspective view of the scope of FIG. 16 showing thefundamental mode of resonance for actuating members;

FIG. 18 is a perspective view of another embodiment of a scope portionof the system of FIG. 1, including a bimorph bender actuator in whichphotodetectors are mounted to a stationary base;

FIG. 19 is a perspective view of another embodiment of a scope portionof the system of FIG. 1, including a tubular piezoelectric actuator;

FIG. 20 is a perspective view of another embodiment of a scope portionof the system of FIG. 1, including a collector waveguide concentricallysurrounding an illumination waveguide; and

FIG. 21 is a planar view of a portion of a scope portion, includingphoton detectors positioned for differentially factoring out ambientlight.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Overview

Referring to FIG. 1, a miniature image acquisition system 10 includes anilluminating subsystem 12, a collector or detector subsystem 14 and insome embodiments a host system 16. The illuminating subsystem 12 emitslight onto an object. The collector/detector subsystem 14 collects ordetects light reflected from the object. The illuminating subsystem 12and collector/detector subsystem 14 are coupled to the host system 16.The host system 16 includes a controller 18 for synchronizing theilluminator subsystem operations and the collector/detector subsystemoperations. The host system 16 also includes a display device 20, a userinterface 21, an image storage device 22, a processor (not shown), andmemory (not shown). The image acquisition system 10 in some embodimentsis configured as a stand-alone device without a host system 16. In sucha stand-alone embodiment the controller 18 and display 20 are part ofthe stand-alone system. In various applications, the miniature imageacquisition system 10 embodies an endoscope, boroscope, bar code readeror another device for acquiring images.

Referring to FIG. 2, the illuminating subsystem 12 includes a lightsource 24, an optical fiber 26, and a fiber deflection drive system 28.The light source 24 emits a continuous stream of light 30 in oneembodiment, and emits a stream of light pulses 32 in another embodiment.When pulses are implemented, the controller 18 sends a control signal 34to the light source 24 to synchronize and control the timing of thepulse emissions.

The light from the light source 24 enters an optical fiber 26 andtravels to a distal portion 36 where the light is emitted toward anobject. The distal portion 36 is deflected and serves as a resonantwaveguide 36. The fiber 26 or at least the distal portion 36 is flexibleto withstand a resonant deflection motion at the distal portion. Thecontroller 18 sends a synchronization signal 38 to the fiber deflectiondrive system 28, which in turn causes the distal portion of waveguide 36to resonate. The resonant motion of the waveguide 36 causes the emittedlight to be scanned over the object along a desired scan path. In someembodiments the control of the fiber deflection drive system 28 is aclosed loop control with a sensor or feedback signal 40 being sent tothe controller 18. In a preferred embodiment the drive system 28 is apiezoelectric drive system. In alternative drive system embodiments, apermanent magnet or electromagnet drive, an electrostatic drive, anoptical drive, a sonic drive or an electrochemical drive are implementedin place of the piezoelectric drive.

Preferably one or more lenses 37 are formed at the distal end of thewaveguide by shaping the distal end. Alternatively, one or more lensesare fused, bonded, mounted or otherwise attached to the distal end(i.e., the distal tip) of the distal end 36. Preferably, the lenses 37do not extend beyond the circumference and diameter of the fiber end 36.The lenses 37 are fixed relative to the distal end 36 and move andchange orientation with the distal end 36. These lenses 37 serves tocollimate the emitted light. Another lens 39, such as a scan lens or anf-theta lens is positioned beyond the distal end 36 of the fiber in thepath of the emitted light to focus the light on the object. In someembodiments the lens 39 is a refractive and/or diffractive opticalelement. such as a gradient refractive index lens. The lenses 37, 39determine the image quality and define the image resolution of thesubsystem 12.

The lens 39 serves as a scan lens and is formed of glass, plastic, oranother waveshaping material such as liquid crystal. The optical powerof the scan lens 39 determines at what distance, if any, an illuminationforms a focal plane. If the emitted light 30/32 is collimated, theresulting image has a resolution approximating the emitted light beamdiameter, resulting in an image with an enormous depth of field.Increasing the power of the scan lens 39 increases the pixel resolutionwhile decreasing depth of field or depth of focus. The focal plane ofthe scan lens 39 depends on its power and location with respect to thedistal tip 58 (see FIG. 5A) and distal lens 37. The focal plane can beadjusted by moving the scan lens 39 axially relative to the distal lens37.

Referring to FIG. 3, in one embodiment a portion 42 of a miniature imageacquisition system 10 includes a collector subsystem 14′ and a retinalscanning display device 20′. Light from the illuminating system 12 (seeFIGS. 1 and 2) is output to an object. Reflected light 44 from theobject is collected at the one or more collector fibers 46 and routeddirectly to a scanning display device 20′. In one embodiment the displaydevice 20′ scans the light onto the retina of a human eye E. In anotherembodiment the display device scans the light onto a projection screen,(e.g., being amplified electro-optically). In still another embodiment(not shown) the light from the collect fiber 46 is sampled and stored byan image storage device 27. The scanning or storage of the collectedlight is synchronized to correlate to the illumination light bycontroller 18.

In some embodiments the collector fiber 46 is deflected by a drivesystem 48 along a common path with the illuminating fiber 26 of theilluminating subsystem 12. The drive system 48 may be the same system asthe illuminating subsystem drive system 28 or may be a separate drivesystem. Preferably the drive system 48 is a piezoelectric drive system.The drive system 48 receives the synchronization signal 38 from thecontroller 18. In embodiments where the collector fiber 46 isstationary, there is no need for a drive system 48.

The scanning display device is of the kind known in the art. Anexemplary device is disclosed in U.S. Pat. No. 5,467,104 issued Nov. 14,1995 for “Virtual Retinal Display” to Furness et al. Another exemplarydevice is disclosed in U.S. Pat. No. 5,694,237 issued Dec. 2, 1997 for“Position Detection of Mechanical Resonant Scanner Mirror” to Melville.

Referring to FIG. 4, in an alternative embodiment the miniatureacquisition system 10 includes a detection subsystem 14″. The detectorsubsystem 14″ includes one or more photon detectors 50. Exemplary typesof photon detectors 50 which may be implemented include photomultipliertubes, silicon and semiconductor based photodetectors, electro-opticallyamplified optical fibers, image storage media (e.g., film) andphotoemissive media. Reflected light impinges on the photon detectors50. The detectors 50 continuously, periodically or aperiodically samplethe reflected light 44 based upon on a sampling signal 52 received fromcontroller 18. The sampling signal 52 correlates in timing to thesynchronization signal 38 output to the illuminating subsystem 12. As aresult, the photon detectors 50 output a continuous signal or a streamof electronic signal pulses corresponding to the sampling of thereflected light 44. In one embodiment an output signal 54 is routed toan image storage device 22 to build and store an image frame of data. Invarious embodiments the image storage device 22 is an analog storagedevice (e.g., film) or a digital storage media. In addition, oralternatively, the same or a different output signal 55 is routed to adisplay device 20 to build and display a frame of image data. Thedisplay device may be any conventional display device, such as a cathoderay tube, liquid crystal display panel, light projector, gas plasmadisplay panel or other display device.

Resonance Modes of the Illuminating Fiber Waveguide

Referring to FIGS. 5A-C the illuminating fiber 26 is shown beinganchored at a point 56 along its length. The length of fiber 26 from theanchor point 56 to the distal tip 58 is referred to as the distalportion 36 which serves as the resonant waveguide. In some embodiments,a short fiber 26 is used in which substantially the entire fiber servesas the resonant waveguide 36, and occurs along the length from theanchor point 56 to the distal end 58. The waveguide 36 is driven by afiber deflection drive system 28 (see FIG. 2) causing the waveguide tobe deflected in a resonant mode.

There are many resonant modes which can be implemented by the drivesystem 28. In every mode, a stationary node occurs at the anchor point56. An anti-node (i.e., point of maximum deflection) occurs along thelength of the waveguide 36. Referring to FIG. 5A, a resonance mode isillustrated in which a stationary node occurs at the anchor point 56 andan anti-node occurs at the distal end 58. The waveguide 36 is shown in aneutral position 60, and at two maximum deflection positions 62, 64.

Referring to FIG. SB, a resonance mode is illustrated in which there aretwo stationary nodes: one at the anchor point 56, and the other at apoint 66 between the anchor point 56 and the distal end 58. An anti-nodeoccurs at point 68 between the two stationary nodal points 56, 66. Thewaveguide 36 is shown in a neutral position 60, and at two maximumdeflection positions 62′, 64′. In various resonance modes, one or morestationary nodes are formed along the length of the waveguide causingthe distal end 58 to swing along an arc 70. Zero up to n anti-nodes alsomay be formed where ‘n’ corresponds to either the number of stationarynodes or one less than the number of stationary nodes.

Referring to FIG. SC, in a preferred resonance mode, a stationary nodeoccurs at the distal end 58 of the waveguide 36. The waveguide 36 isshown in a neutral position 72, and at two maximum deflection positions74, 76. Although no additional stationary nodes are shown between thestationary nodes at the anchor point 56 and at the distal end 58, invarious embodiments additional stationary nodes do occur between suchpoints 56, 58. To maintain a node of natural vibratory resonance at thedistal tip of the waveguide, the mass and damping at the distal end 58is a controlled design feature. Typically, a small increase in both massand damping from the waveguide of uniform geometry and materialproperties is sufficient. One embodiment is the addition of a more densecollimating lens 37 to the tip of the waveguide 36.

FIG. 5D shows a side view of the distal end 58 (e.g., lens 37) for theresonance modes having a stationary node at the distal tip 58. Shown area neutral orientation 78 corresponding to the neutral position 72 of thewaveguide 36, a maximum angular orientation 80 in one directioncorresponding to the maximum deflection position 74, and another maximumangular orientation 82 in another direction corresponding to the maximumdeflection position 76. As illustrated, a center point 84 is generallystationary for each orientation. In a precise illustration (not shown),the end 58 is slightly offset along the axis 88 (e.g., z-axis of FIG.5D) of the waveguide 36, as the waveguide is deflected. However, thereis no movement off the axis (along the x-axis or y-axis), only a changeof orientation about the axis from orientations 78, to 80 to 78 to 82and back to 78. Such changing orientation during the deflection of thewaveguide 36 results in emission of a ray 90 of light in a directiongenerally perpendicular to a distal face of the lens 37. The ray 90scans an arc 92 during the changing orientation of the distal end 58 andlens 37. Ray 90′ is perpendicular to the lens 37 in position 82. Ray 90″is perpendicular to the lens 37 in position 80. Such arc 92 defines thefield of view for the illuminating subsystem 12.

An advantage of placing a stationary node at the distal end 58 of thewaveguide 36 is that the diameter of the endoscope or other illuminatingdevice need not be enlarged to encompass a swinging arc 70 as in theresonant modes shown in FIGS. 5a and 5 b. By fixing the distal end inX-Y space, rather than swinging it as a point source of light along aline or arc in X-Y space, optical distortions and aberrations arereduced. Further, rather than moving the distal end along an arc 70 todefine the field of view, the position of the distal end 58 issubstantially fixed while the orientation of the distal end changes withthe resonating motion of other regions of the resonating waveguide. Thechanging angular orientation of the fiber distal end 58 defines thewidth of the field of view which is scanned (i.e., defines the arc 92).

Temporally Spaced Pixel Acquisition Method

One of the distinctions of the miniature image acquisition system 10over prior art devices is that pixel resolution is determined by theillumination spot size, rather than a sampled spot size (e.g., by thesampling area of a sensor or collector fiber). In applicant's method,the illumination spot size, rather than the sampled area size,determines the pixel resolution. As a result, the detector size does noteffect image resolution. Thus, one large detector or a plurality ofsmaller detectors are used according to the desired functionality,(e.g., color, stereo, high contrast).

Referring to FIG. 6A, conventionally a fiber illuminates an entireobject area 95, either all at once or by scanning the object to form animage plane 96. The image plane is a spatial area of image pixels. Insome conventional techniques the entire object area 95 is illuminatedconcurrently, while a small spatial area 97 of the image plane 96 issampled to acquire an image pixel. In other conventional techniques, alight is scanned over the object to illuminate a changing portion 98 ofthe object. A small spatial area 97 within the illuminated area 98 issampled to acquire the pixel. These conventional techniques arecharacterized by (i) a small spatial area being sampled which becomesthe acquired pixel and determines the pixel resolution, and (ii) anillumination area larger than the sampled area for any given sample.

Referring to FIG. 6B, a different technique is performed. According toan aspect of this invention, instead of illuminating a large area andsensing a small pixel area, a small pixel area is illuminated and alarge area is sampled. Specifically, the light emitted by waveguide 36(of FIG. 2) illuminates a small area 99 at some given time whichcorresponds to the pixel being acquired. The area 100 sampled by thedetectors 50 or collector fiber 46 is larger than the illuminated spotsize 99. This distinction is significant in that conventional techniquesdefine their pixel and pixel resolution by the sampled area determinedby their sensor (e.g., the sample spot size). According to thistechnique the pixel resolution is defined by the size of theillumination spot. The size of the illumination spot is preciselycontrolled by the waveguide 36 with lenses 37 and 39.

To have the illumination spot size correspond to the pixel to besampled, there is a time synchronization between the illumination andthe sampling. This synchronization is not to synchronize sampling to aspecific location within an image plane as in the conventional method,but instead is a time synchronization to an illumination signal orpulse. For example, photon detectors 50 in one embodiment detect lightfrom an entire object at any given time. The light detected at suchdetectors 50 is synchronized to a specific emission of light to obtainthe pixel corresponding to that emission. In effect the spatialrelationship is factored out of the sampling process. Instead, the pixellocation is inherently known by knowing the position of the illuminatingspot at the corresponding time.

By knowing the position of the scanned light spot for every instant intime, the image is generated one pixel at a time, much like a videosignal. For example, by scanning image lines at 15.75 kHz and detectingthe light at 12.5 MHz time resolution, the pixel stream composing a RGBcolor image at VGA resolution (640×480) is generated at video rates (60Hz).

Using the time synchronization approach, a pixel is acquired within agiven window of time. Because a pixel is detected as the received lightwithin a window of time, the photons detected at such time window comefrom the illuminated spot. Further, by using multiple sensors, a commonmode rejection scheme is implemented to filter out ambient light anddetect the illuminated light reflected back from the object.

An advantage of this approach is that the confocal problem occurring inthe prior art systems is avoided. For example to define the pixel timewindow sizes using a typical VGA video rate, one pixel is collectedevery 40 nanoseconds. For the light of one pixel to interfere with thelight from another pixel, the light of the first pixel would have tobounce around approximately 20 feet on average (because light travelsabout 1 foot/nanosecond). For typical applications such light would haveto bounce around in a space less than one cubic inch. That correspondsto approximately 240 reflections. It is unlikely that the light from onepixel will make 240 reflections before the photon is absorbed or thephoton flux is highly attenuated. Thus, the confocal problem is notsignificant.

Referring to FIG. 7, the waveguide 36 resonates while light 30/32 isemitted toward lens 39. The lens directs the light toward a specificspot location on a target object. At one extreme end of the waveguidedeflection, a spot A of the object is illuminated. As the deflectioncontinues the waveguide reaches a neutral position at which spot B isilluminated. Still continuing the waveguide reaches an opposite extremeat which spot C is illuminated. The light which illuminates spot C has apeak intensity radius R. Such intensity trails off outside the radiusand is considered insignificant. Accordingly, a single scan linetraverses a path from spot A to spot C. In some embodiments the fiberdeflection system 28 is a linear scanning system which scans along aline. In another embodiment, the system 28 scans along a rectilinear orradial raster pattern. In still other embodiments, a spiral scanningpattern is implemented by the drive system 28, in which the radius ofthe spiral varies to trace an area of an object. The arc formed bypoints A and C determines the field of view, and may span toapproximately 180 degrees. The distance of spots A,B, and C isdetermined by the lenses 37, 39 and may be substantially greater thanthe distance between the lenses 37, 39.

Referring to FIG. 8, an exemplary synchronization signal 38 receivedfrom the controller 18 is shown for synchronizing the drive system 28.The angular displacement 102 (e.g., orientation) of the distal end 56and lens 37 also is shown in FIG. 8. Lastly, the position 10 of theilluminating spot is shown as it is traced along a scan line of theobject. An exemplary scan line, for example occurs from time T₁ to T₂.The next scan line (for an interlaced scanning embodiment) occurs fromtime T₂ to T₃. At various times during the scanning motion theillumination spot is over spots A, B and C. During the first scan line,spot A is illuminated at time T_(A1). Spot B is illuminated at timeT_(B1). Spot C is illuminated at time T_(C1). For the subsequent scanline occurring from time T₂ to T₃, a corresponding spot C is encounteredfirst and illuminated at time T_(C2). After corresponding spot B isilluminated at time T_(B2). Then corresponding spot A is illuminated attime T_(A2).

For a VGA resolution implementation, the time from T₁ to T₃ is 63.5 μs(microseconds). Thus, the time from T₁ to T₂ is 31.75 μs. The time fromT_(A1) to T_(C1) is less than 31.75 μs. Specifically, for a VGA standardeach scan line is divided into 800 equally times pixels. Thus, eachpixel spans 40 ns (nanoseconds). Accordingly, the time from T_(A1) toT_(C1) is 25.6 μs.

FIGS. 9 and 10 depict an implementation in which the emitted light is acontinuous stream of light 30 which moves along a scan line 106. In theFIG. 9 implementation the photon detectors 50 are continuously activewith a pertinent portion (T_(A) to T_(C)) being divided equally into ‘N’pixels 108. For the VGA standard there is a 40 ns sampling time perpixel. For another standard, a different sampling time may be used. Inthe FIG. 10 implementation the photon detectors 50 are sampledperiodically. Each sampling corresponds to an acquired pixel 110. ‘N’pixels are acquired per scan line 106. In one embodiment, each samplingoccurs over a duration of 20 ns. The time between midpoints of eachsampling interval is 40 ns. for a VGA standard. For such standard, acorresponding sampling time interval is 10 ns. Again alternativesampling times and time intervals may be used.

Referring to FIGS. 2 and 11, in one embodiment the illumination system12 emits pulses 112 of light 32 periodically during scanning of a scanline 114. The photon detectors 50 (see FIG. 4) are synchronized tosample the object or an area of the object including at least theilluminated spot at a time to capture the reflected light correspondingto a known spot. The sampling interval, i, corresponding to a spot(e.g., spot B) spans a time period 116 which is any of greater than,equal to or less than the time interval 118 of the light pulse for thespot. A typical time for the sampling interval 118 is 20 ns, and mayvary. In still another embodiment (not shown) the detectors 50continuously detect the reflected light as described regarding FIG. 9,while 10 the sampling results are correlated to the emitted light pulses112.

By maintaining the illumination and/or detector at a fixed frequency,(e.g., {fraction (1/40)} ns=12.5 MHz), the signal to noise ratio can beincreased significantly with amplification at only the fixed frequency.Thus, noise at all other frequencies can be eliminated by filtering athigher and lower frequencies.

Physical Embodiments

Referring to FIG. 12, a scope portion 120 of the image acquisitionsystem 10 is shown in which the waveguide 36 and an actuator 125 of thefiber deflection system 28 are enclosed in a protective sheath 122. Thescan lens 39 seals the end! of the scope. The focal plane of the scanlens 39 depends on its power and location with respect to the fiber tip58 and distal lens 37. The focal plane can be adjusted by moving thelens 38 axially relative to the distal lens 37.

For single axis 126 scanning the waveguide 36 is deflected within thesheath 122 by the actuator 125. The base of the cantilevered waveguideis anchored to the distal end of the actuator 125 creating the firststationary ‘node’ of the vibratory resonance. Any of the resonance modesdescribed with regard to FIGS. 5A-D may be implemented. For two axisscanning a second actuator 124 deflects the scope 120 along an axis 130(see FIG. 14). In some embodiments, however, the actuators 124 and/or125 produce a nonlinear actuation of the waveguide to induce twodimensional motion, such as along a spiral pattern.

Referring to FIG. 13, pairs of red, green, and blue photodetectors 50are shown within the distal anchoring surface of actuator 125 to capturecolor images in quasi-stereo. The photodetectors temporal bandwidth ishigher than the rate of pixel illumination to avoid limiting contrast orresolution. For example, such photodetector bandwidths are ≧12.5 MHz forVGA and ≧19.8 MHz for sVGA video standards.

Many silicon-based photodiodes that are smaller than 1 mm diameter havesufficient bandwidth in the visible spectrum. For increased noisereduction, the photodetectors are combined with integratedpre-amplifiers in a Micro-optical Electro Mechanical Systems (‘MEMS’)fabrication process. An alternative approach is to guide the light tothe proximal end of the scope within the outer concentric layer orspecialized cladding of the single fiberoptic cantilever, or by usingone or more large core (multimode) optical fibers to capture thebackscattered light. Such arrangements allow the photodetectors to be atthe proximal end of the scope, which would be less affected by theenvironmental factors, physical space limitations, and the possiblecomplications brought on by the desire for disposability and/orsterilizability.

Referring to FIGS. 15A-C, a ‘MEMS’ embodiment of the scope portion 120′of system 10 is shown. In such embodiment the optical waveguidestructure for mechanically resonant vibratory motion is batch fabricatedusing silicon micromachining techniques, producing a MEMS scanner. Insuch embodiment the actuators 124,125, detectors 50 and additional lightconduits (not shown) also are fabricated using the same MEMS processesresulting in an integral structure. A microlens 37 and scan lens 39 alsoare fabricated using the same MEMS processes, or a separateinjection/pressure molding or MEMS process, then is attached to theother MEMS structure. Additional optical and displacement sensors alsomay be incorporated in the scope 120′ for long-term control of thescanning stability. In such embodiment the MEMS cantilevered waveguide36′ is being illuminated from an optical fiber 26 that is bonded withina V-groove 132 of an underlying substrate 134.

Referring to FIGS. 16 and 17, in an alternative embodiment of a scopeportion 120″, the optical fiber 26 extends through a tubular mechanicalsupport 140, which serves as a conduit for electrical wires and opticalfiber(s), and support a surrounding protective sheathing (not shown). Apiezoelectric bimorph bender 142 is cantilevered out from the support140, along with the electrical wires 144 and optical fiber 26. Thebender 142 serves as the actuator of the fiber deflection drive system28 (see FIG. 2).

At a distal end of the bender 142 is a disk structure 146 that supportsthe cantilevered fiberoptic scanning waveguide 36 used to generate aslow scan axis 14.5.

On the disk structure 146 are the photon detectors 50, such ascommercial 0.1 mm diameter photodiodes that are bonded directly onto thedisk. At the center of the detectors 50, surrounding a base of thewaveguide 36 is a piezoelectric ring 48 which drives the fiberopticwaveguide 36 into vibratory resonance. The scanning motion of the twopiezoelectric actuators 142, 148 produces scanning in two orthogonaldirections 145, 147 simultaneously. The fundamental mode of resonance isshown in FIG. 17 for both scan axes 145, 147.

Referring to FIG. 18, in a similar scope 120′″ embodiment rectilinearscanning motion in a reduced diameter is achieved by using a second modeof vibratory resonance for both scan axes 145, 147. Like in the FIG. 17embodiment the bimorph bender 142 is deflected. In this second mode,however, another stationary node occurs in the scope. Specifically, inthe FIG. 18 embodiment a second node of vibratory motion occurs at thedistal end of the vibrating elements 142, 36. For example, theadditional mass of a collimating lens 37 at the fiber tip allows themotion of the scanned beam to be rotational without translation. Note,the photon detectors 50 are located a stationary base 150 of the scope120′″.

Referring to FIG. 19, in yet another scope 120″″ embodiment, tworotationally symmetric scanning motions of the waveguide 36 are achievedusing a single actuator 152. For either of a circular scanning andradially scanning implementation, actuator 152 is a tube piezoelectricactuator.

Referring to FIG. 29, in yet another scope 120″″′ embodiment, theilluminating waveguide 36 is concentrically surrounded by a collectorwaveguide 160. In this embodiment the collector waveguide 160 moves withthe deflector waveguide 36.

Stereo and Color Viewing

The various scope embodiments may be adapted to enable stereoscopic andcolor viewing. Stereo imaging for example is implemented by providingmatched pairs of detectors which are physically separated and whichsynchronously sample the reflected light. This is a substantialadvantage over prior systems in which a separate scope is used forstereoscopic viewing. In contrast, a single illuminating fiber is usedto obtain stereoscopic viewing.

Color viewing is implemented by including photon detectors sensitive torespective ranges of wavelengths corresponding to the desired colors.Referring to FIG. 13, matched pairs of red, green and bluephotodetectors are included for stereoscopic color imaging.

In the various embodiments the photon detectors 50 may be single ormultielement photon detectors. Referring to FIG. 21, photon detectors50′, 50″ are mounted at different axes so as to differentially factorout photons of ambient light (and highly scattered back reflections fromthe illumination of the target), as distinct from the photons emitted bythe illuminating fiber 26 and reflected directly back by the object. Inparticular, common mode rejection of ambient light is implemented forembodiments in which the scope is exposed to ambient light having anintensity which is significant relative to an intensity of illuminatedlight 30/32.

Applications

A. Endoscope/Boroscope/Catheter

Small overall diameter, best mode is ≦3 mm,

Extremely flexible shaft, containing a single optical fiber,

High resolution, theoretical limit is estimated to be 5 μm,

Very wide Field of View (FOV) is achieved, (beyond the standard 45°, upto approximately 180 degrees).

Red (R), Green (G), and Blue (B) full color detection,

Stereo image detection accomplished in either two ways:

matched pairs of stereoscopic R,G,B light detectors helping to enhancethe topographical contrast feature inherent in scanned illuminationsystems, quasi-stereo.

dual image generators, diameter ≦6 mm in best mode, allowingtrue-stereo.

Video rates of image display (60 Hz refresh rate is standard),

Low cost, potentially disposable, sterilizable,

Low power, resonant scanner operation,

Simple design of few moving parts,

Can be applied to high power laser, visible, UV or IR illumination, forsuch medical procedures as photodynamic therapy, laser-inducedfluorescence, laser surgery, IR imaging in blood, etc.,

Can be applied to high power, short-pulsed UV, visible, or IRillumination for such medical applications as measuring distancesbetween the scope and tissue (range finding and true 3D imaging),multi-photon fluorescence imaging, and fluorescent lifetime imaging,

Small size and flexibility allows the image generator to be retrofittedto existing endoscopes (cannulas), flexible sheaths, or attached tosurgical or diagnostic tools,

Flexibility in bending as well as rotation with single fiber axiallysymmetric optical coupling

The acquired photoelectric signal is directly compatible with videosignal inputs of RGB video monitors, especially having multi-synchcapabilities,

The backscattered light is guided by optical fibers directly from thedistal end to the viewer's eye at the proximal end eliminating the needfor photodetectors at the distal end. In addition to a standard videodisplay monitor, the image is displayed in one embodiment by a retinalscanning device without the need for electronic signal conversion

B. Other Applications: Remote Optical Sensing, Robotic eyes placed atthe finger-tips of the robotic hands or graspers, Long-Term ProcessMonitoring; Eye Tracker, Bar Code Reader, Range Finder,microlithography, visual displays, optical inspection, and lasersurgery.

Meritorious and Advantageous Effects

An advantage of the invention is that flexibility of the fiber, a widefield of view and high resolution are achieved even for small, thinscopes due to the method in which pixels are obtained, the presence ofthe lenses and the manner of driving the fiber. Because pixels aremeasured in time series and not in a 2-D pixel array, it is notmandatory to have small photon detectors. The size of the detector isnot critical as in the prior scopes where many small detectors spanned alarge area. Therefore, a scope of this invention can be made smallerthan existing scopes while using fewer photon detectors that are largerthan the pixel detectors of standard scopes. According to the invention,as little as one photon detector may be used for monochrome imageacquisition and as few as single red, green and blue detectors may beused for full-color imaging. By adding matched stereo-pairs of red,green and blue detectors, the advantage of quasi-stereo imaging isachieved accentuating topography in the full-color images.

An advantage of the embodiment in which an operator directly viewsphotons reflected from a scanned object is that images of higher spatialresolution, contrast and temporal resolution are achieved. Such viewingmethod differs from conventional image acquisition systems and otherembodiments of the invention in which the scattered light impinges uponphoton detectors, which then transmit the photon stream. Such photondetectors include photomultiplier tubes, silicon-based photodetectors,image storage media (e.g., film) and photoemissive media. Such photondetection is all intermediary step. By eliminating the intermediarystep, the spatial resolution, contrast, color fidelity, and temporalresolution are improved. Such improvement occurs because the limitedbandwidth of the detectors and the introduction of noise into the imagesignal by the detectors are avoided. Further, resampling andredisplaying of the object image do not occur so the mismatching of theresampled signal to the spatial and temporal sampling of the human eyedoes not occur and thus does not further degrade the image. Theshortcomings introduced by the photon detectors are avoided bydisplaying each pixel as it is acquired.

According to another advantage of the invention, a high resolution, highfield of view, scanning, flexible fiber device is achieved. Inparticular by locating the fiber resonant node at the distal end of theresonating waveguide portion of the fiber, a wide scanning angle isachieved in a relatively small fiber movement area. This allows for awide field of view. By using a small spot size and by time capturing thedetected light in correlation to the illumination light, a high pixelresolution is achieved. With the small size and low power consumption, alow cost, disposable scanning device is achieved.

Although a preferred embodiment of the invention has been illustratedand described, various alternatives, modifications and equivalents maybe used. For example, in some embodiments, a sensor is mounted at thetip of the fiberoptic scanner to detect the fiber position and aid incontrolling the scan pattern using an electromagnetic, electrostatic.electromechanical, optical, or sonic control.

In alternative embodiments, a variable or non-rectilinear scan patternis implemented, such as an elliptical pattern with varying radii andcentroid location. For example, such customized scan patterns such asrotating linear or radial patterns are desirable for single actuator,small sized eye-tracking and bar-code reading implementations.

Alternative methods for implementing a second slower, orthogonalscanning axis include moving a mirror, lens(es), gratings, orcombinations of the same. Such optical components are located betweenthe fast scanning resonant fiber and the target object.

In some embodiments the tip of the fiber 26 is tapered (i) to reduce themass of the fiber tip for increased scan amplitude, (ii) to reducephysical range of scan motion. and/or (iii) to reduce effective pointsource size of light emission.

In some embodiments polarization maintaining illumination components andpolarization filters are included to reject backscattered light that hasundergone multiple scattering and color shifting. In some embodimentsthe wave guide is a cantilever having a light source at the distal endof the waveguide where light is emitted.

Although in the preferred embodiment visible light is emitted anddetected, in alternative embodiments the emitted and detected light isultraviolet light, infrared. In some embodiment sensors are includedwhich provide feedback to a drive system controller which in responseadjusts the deflection of the cantilever. As a result, the deflection ofthe cantilever is adjusted and controlled.

In some embodiments true stereoscopic viewing is achieved by eitheradding another scope and processing the required image parallax forhuman viewing, or by adding an axial measurement from the scope to thetarget by range finding at each pixel position. Such axial measurementis a third image dimension which is processed to generate stereo views.For example, signals from matched pairs of detectors 50 are processed bythe controller to detect phase difference in the returning light. Suchphase difference corresponds to a range distance of a target object fromthe scanner. In one implementation a modulated laser infrared sourceoutputs infrared light in the GHz frequency range. Fast photon sensorsdetect the returning infrared light. The phase difference in themodulation between the illuminated infrared light and the collectedinfrared light allows determination of distance to resolutions of ≦1 mm.In particular, for an embodiment in which the light is modulated at 1GHz, the light travels 1 foot between pulses or about 1 mm per degree ofthe 360 degrees of phase difference between pulses.

Therefore, the foregoing description should not be taken as limiting thescope of the inventions which are defined by the appended claims.

What is claimed is:
 1. A method for acquiring an image of a targetsurface, comprising the steps of: outputting a beam of light from aresonant fiber waveguide, the waveguide scanning the output beam along ascan path; focusing the beam with a scan lens onto a target surfacebeing scanned, wherein at a given time the beam is focused to impinge ona spot of the target, the spot being an illuminated spot, theilluminated spot varying with time as the beam is scanned onto thetarget surface; detecting light reflected from an area of the targetsurface which is greater than an area defined the illuminated spot;correlating the given time at which the beam focuses onto theilluminated spot with the detected reflected light to acquire a pixel ofthe image, wherein resolution of the pixel corresponds to the areadefined by the illuminated spot, wherein over time a plurality of pixelsare acquired.
 2. The method of claim 1, further comprising the step ofcollimating the light output from the resonant fiber waveguide.
 3. Themethod of claim 1, further comprising the step of: deflecting thewaveguide in a resonant mode in which a distal tip of the waveguide is astationary node, the distal tip changing orientation to angularly scanthe output beam.
 4. The method of claim 1, in which the step ofdetecting is performed by a photon detector which is stationary relativeto a motion of the waveguide which occurs during scanning along the scanpath.
 5. The method of claim 1, in which the step of detecting isperformed by a photon detector which does not move synchronously withthe resonant waveguide.
 6. The method of claim 1, in which the scan pathis a raster scan path defined by a first fast scanning axis and a secondscanning axis, and in which the waveguide resonates to deflect theoutput beam along the fast scanning axis.
 7. The method of claim 6, inwhich the waveguide resonates to deflect the output beam simultaneouslyalong the fast scanning axis and the second scanning axis.
 8. The methodof claim 1, in which the step of detecting is performed by a photondetector which is stationary relative to the fast scanning axis.
 9. Themethod of claim 1, in which the scan path is a spiral scan path.
 10. Themethod of claim 1, in which the scan path is a radial scan path.
 11. Themethod of claim 1, in which the step of detecting comprises the stepsof: collecting reflected light at an optical fiber; routing thecollected light to a scanner; scanning the collected light with thescanner onto a viewer's eye which detects the collected light.
 12. Themethod of claim 11, in which the step of detecting further comprisesoptically amplifying the collected light by adding photons havingproperties which are the same as photons of the collected light.
 13. Themethod of claim 1, in which the step of detecting comprises the stepsof: collecting reflected light at an optical fiber; routing thecollected light to a scanner; scanning the collected light with thescanner onto a display screen; wherein the reflected light scanned ontothe display screen is not stored or sampled.
 14. The method of claim 13,in which a portion of the reflected light is scanned onto the displayscreen without being stored or sampled, while another portion of thereflected light is split off by a beam splitter and routed for storage.15. The method of claim 1, in which the beam of light is a first beam oflight, and further comprising, prior to the step of outputting the stepsof: generating a second beam of light of a first color and a third beamof light of a second color; and combining the second beam and the thirdbeam before entering the resonant waveguide, the combined second beamand third beam forming the first beam which is output from the resonantwaveguide.
 16. The method of claim 1, in which the output beam of lightis a sequence of light pulses, and wherein the step of detecting issynchronized with the sequence of light pulses, the detected reflectedlight at said given time corresponding to a given light pulse and saidacquired pixel.
 17. The method of claim 1, in which the step ofoutputting comprises outputting a beam of ultraviolet light, and thestep of detecting comprises detecting light reflected from said area.18. The method of claim 1, in which the step of outputting comprisesoutputting a beam of infrared light, and the step of detecting comprisesdetecting infrared light reflected from said area.
 19. A system foracquiring an image of a target surface, comprising: a light source whichemits light; a flexible, optical waveguide which receives the emittedlight and directs the light toward a target surface, wherein at a giventime the light impinges on a spot of the target surface, the spot beingan illuminated spot; an actuator which deflects the waveguide into aresonant motion, the directed light tracing a scan path along the targetsurface; a photon detector having an active viewing area of the targetsurface which exceeds size of the illuminated spot; and a correlatorwhich correlates sampling time of the photon detector with the light asthe light traces a scan path, wherein pixels are acquired of an image ofa portion of the target surface, wherein resolution of each one pixel ofthe acquired pixels corresponds to the size of the illuminated spot. 20.The system of claim 19, further comprising a display device coupled tothe photon detector for displaying the image in real time as pixels areacquired.
 21. The system of claim 20, in which the display devicedisplays the image without resampling an output signal of the photondetector said output signal corresponding to a sequence of acquiredpixels.
 22. The system of claim 19, wherein the photon detectorgenerates an output signal corresponding to a sequence of acquiredpixels, and further comprising means, coupled to the photon detector forstoring the acquired pixels.
 23. The system of claim 19, furthercomprising a focusing lens spaced off the distal tip of the waveguidewhich focuses light onto the target surface as the light traces a scanpath.
 24. The system of claim 23, further comprising a collimating lensat a distal tip of the waveguide for collimating light directed towardthe focusing lens.
 25. The system of claim 19, further comprising meansfor driving the actuator to deflect the waveguide in a resonant mode inwhich a distal tip of the waveguide is a stationary node, the distal tipchanging orientation to angularly scan the light.
 26. The system ofclaim 19, in which the scan path is a spiral scan path.
 27. The systemof claim 19, in which the scan path is a radial scan path.
 28. Thesystem of claim 19, in which the scan path is a first scanning axis of araster scan path having the first fast scanning axis and a secondscanning axis, and in which the waveguide resonates to deflect theoutput beam along the first scanning axis.
 29. The system of claim 28,in which the waveguide resonates to deflect the output beamsimultaneously along the first scanning axis and the second scanningaxis.
 30. The system of claim 29, in which the actuator is a firstactuator and further comprising a second actuator which causes the lightto move along the second scanning axis.
 31. The system of claim 29, inwhich the photon detector is mounted to a base which is stationaryrelative to the first scanning axis.
 32. The system of claim 19, inwhich the photon detector is mounted to a base which is stationaryrelative to the scan path.
 33. The system of claim 19, in which thelight source is a first light source emitting light of a first color,the system further comprising a second light source emitting light of asecond color, and a combiner which combines the light emitted from thefirst light source and the second light source, the combined light beingreceived by the waveguide and being directed toward the target surface.34. The system of claim 19, in which the photon detector comprises aplurality of photon detectors positioned and sampled for stereoscopicviewing of the target surface.
 35. The system of claim 19, in which thephoton detector comprises a plurality of photon detectors and lightfilters for detecting prescribed wavelengths and corresponding colors oflight.
 36. The system of claim 19, in which the photon detectorcomprises a plurality of photon detectors and light filters fordetecting prescribed polarizations.
 37. The system of claim 19, in whichthe photon detector comprises a plurality of photon detectors positionedand sampled to implement common mode rejection of ambient light, whiledetecting photons of light which are emitted by the waveguide thenreflected by the target surface.
 38. The system of claim 23, in whichthe waveguide and actuator are enclosed in a sheath which is sealed bythe focusing lens.
 39. An image acquisition system, comprising: a lightsource which emits light; an optical waveguide which receives theemitted light and directs the light toward a target surface, wherein ata given time the light impinges on a spot of the target surface, thespot being an illuminated spot; an actuator for deflecting the waveguidein a resonant mode, wherein the light traces a scan path along thetarget surface; a collector fiber which collects light over an area ofthe target surface which includes and exceeds an area of the illuminatedspot; a scanning device optically coupled to the collector fiber whichscans the collected light onto a second surface; wherein a given time atwhich the light impinges on the target surface is synchronized with thecollection of light and scanning of collected light to acquire a portionof an image of the target surface, and wherein image resolution isdetermined by the area of the illuminated spot, wherein the collectorfiber collects photons of light and the second surface receivescollected photons of light directly, as distinguished from the secondsurface receiving a sampled representation of the collected light. 40.The system of claim 39, in which the scanning device is a retinalscanning device which scans the collected light onto a retina of aviewer's eye, the retina being the second surface.
 41. The system ofclaim 39, in which the scanning device scans the collected light onto adisplay screen in real time as pixels are acquired, the display screenbeing the second surface.
 42. The system of claim 39, furthercomprising: a first lens at a distal tip of the waveguide forcollimating light; a second lens spaced off the distal tip of thewaveguide and away from the first lens which focuses light onto thetarget surface as the light traces a scan path.
 43. The system of claim39, in which the actuator is a first actuator and the scan path is afirst scanning axis; the system further comprising a second actuator forscanning light along a second scanning axis.
 44. The system of claim 39,in which the actuator deflects the waveguide in a resonant mode in whicha distal tip of the waveguide is a stationary node, the distal tipchanging orientation to angularly scan the light along the scan path.45. The system of claim 39, in which the collector fiber is stationaryrelative to a motion of the waveguide.
 46. The system of claim 39, inwhich the light source is a first light source emitting light of a firstcolor, the system further comprising a second light source emittinglight of a second color, and a combiner which combines the light emittedfrom the first light source and the second light source, the combinedlight being received by the waveguide and being directed toward thetarget surface.
 47. The system of claim 39, in which said light isultraviolet light and wherein the light source emits ultraviolet light.48. The system of claim 39, in which said light is infrared light andwherein the light source emits infrared light.
 49. A medical apparatusfor acquiring an image of a target surface, comprising: a light sourcewhich emits light; a flexible, optical waveguide which receives theemitted light and directs the light toward a target surface, wherein ata given time the light impinges on a spot of the target surface, thespot being an illuminated spot; an actuator which deflects the waveguideinto a resonant motion, the directed light tracing a scan path along thetarget surface; a photon detector having an active viewing area of thetarget surface which exceeds size of the illuminated spot; and acorrelator which correlates sampling time of the photon detector withthe light as the light traces a scan path, wherein pixels are acquiredof an image of a portion of the target surface, wherein resolution ofeach one pixel of the acquired pixels corresponds to the size of theilluminated spot.
 50. The apparatus of claim 49, further comprising adisplay device coupled to the photon detector for displaying the imagein real time as pixels are acquired, in which the display devicedisplays the image without resampling an output signal of the photondetector said output signal corresponding to a sequence of acquiredpixels.
 51. The apparatus of claim 49, further comprising a focusinglens spaced off the distal tip of the waveguide which focuses light ontothe target surface as the light traces a scan path.
 52. The apparatus ofclaim 49, further comprising means for driving the actuator to deflectthe waveguide in a resonant mode in which a distal tip of the waveguideis a stationary node, the distal tip changing orientation to angularlyscan the light.
 53. An endoscopic device for acquiring an image of atarget surface, comprising: a light source which emits light; aflexible, optical waveguide which receives the emitted light and directsthe light toward a target surface, wherein at a given time the lightimpinges on a spot of the target surface, the spot being an illuminatedspot; an actuator which deflects the waveguide into a resonant motion,the directed light tracing a scan path along the target surface; aphoton detector having an active viewing area of the target surfacewhich exceeds size of the illuminated spot; and a correlator whichcorrelates sampling time of the photon detector with the light as thelight traces a scan path, wherein pixels are acquired of an image of aportion of the target surface, wherein resolution of each one pixel ofthe acquired pixels corresponds to the size of the illuminated spot. 54.The system of claim 53, further comprising a display device coupled tothe photon detector for displaying the image in real time as pixels areacquired, in which the display device displays the image withoutresampling an output signal of the photon detector said output signalcorresponding to a sequence of acquired pixels.
 55. The system of claim53, further comprising a focusing lens spaced off the distal tip of thewaveguide which focuses light onto the target surface as the lighttraces a scan path.
 56. The apparatus of claim 53, further comprisingmeans for driving the actuator to deflect the waveguide in a resonantmode in which a distal tip of the waveguide is a stationary node, thedistal tip changing orientation to angularly scan the light.
 57. Amedical apparatus, comprising: a light source which emits light; anoptical waveguide which receives the emitted light and directs the lighttoward a target surface, wherein at a given time the light impinges on aspot of the target surface, the spot being an illuminated spot; anactuator for deflecting the waveguide in a resonant mode, wherein thelight traces a scan path along the target surface; a collector fiberwhich collects light over an area of the target surface which includesand exceeds an area of the illuminated spot; a scanning device opticallycoupled to the collector fiber which scans the collected light onto asecond surface; wherein a given time at which the light impinges on thetarget surface is synchronized with the collection of light and scanningof collected light to acquire a portion of an image of the targetsurface, and wherein image resolution is determined by the area of theilluminated spot, wherein the collector fiber collects photons of lightand the second surface receives collected photons of light directly, asdistinguished from the second surface receiving a sampled representationof the collected light.
 58. An endoscopic device, comprising: a lightsource which emits light; an optical waveguide which receives theemitted light and directs the light toward a target surface, wherein ata given time the light impinges on a spot of the target surface, thespot being an illuminated spot; an actuator for deflecting the waveguidein a resonant mode, wherein the light traces a scan path along thetarget surface; a collector fiber which collects light over an area ofthe target surface which includes and exceeds an area of the illuminatedspot; a scanning device optically coupled to the collector fiber whichscans the collected light onto a second surface; wherein a given time atwhich the light impinges on the target surface is synchronized with thecollection of light and scanning of collected light to acquire a portionof an image of the target surface, and wherein image resolution isdetermined by the area of the illuminated spot, wherein the collectorfiber collects photons of light and the second surface receivescollected photons of light directly, as distinguished from the secondsurface receiving a sampled representation of the collected light.